Have you noticed how when you buy the ticket there's no mention of the plane you'll actually fly in and no guarantee that it won't be swapped 45 minutes before takeoff?
I'm saying that looking from a different perspective. As a tall person I would rather fly in planes I know to have better leg room or where I can pick an emergency exit seat. So many times the plane was changed just before boarding and my "emergency exit seat" turned into a regular cramped one because of the different seating arrangement.
So I'll be skeptic of the fact that the market can actually support tickets prices based on the plane model. Unless an airline guarantees the plane model you book your flight on or exclusively uses a specific model then pricing based on the plane used is about as achievable as pricing based on the revision of circuit breakers used in the cockpit.